1. Technical Field
This invention is concerned with nonwoven fabrics and more particularly with a multiaxial nonwoven fabric in which a multiplicity of selected continuous yarns are assembled in a specified lay pattern by mechanical interlocking. The invention further relates to a method of and an apparatus for producing such multiaxial fabric.
By the term multiaxial nonwoven fabric used herein is meant a fabric designed to have its constituent yarns intersected in two or more different axes and even in a weftwise axis.
2. Prior Art
Certain nonwoven fabrics have been developed and marketed, one of which is formed of a number of parallel continuous yarns obliquely crossed and adhesively bonded onto a substrate such as paper, film, aluminum foil or cloth. Another fabric is of a triaxial structure having bound an additional group of arranged warps. Both fabrics are formed typically by a method in which the basic or constituent yarns are allowed to reciprocally run at right angle to the path of travel of a conveyor belt and when brought into hooking engagement, upon arrival at their turning points, with two arrays of pins each located on and along one longitudinal edge of the belt, they are crossed obliquely with one another.
In such prior fabrics, however, the basic yarns each are oriented in the shape of an isosceles triangle when one vertex is taken against the base between the two other vertices. These fabrics, though physically adequate in both a warp and an oblique direction, are mechanically weak and dimensionally unstable in a weft direction.
To cope with the above problems, the conveyor belt is required to travel at low speed so as to reciprocate the basic yarns while being held obliquely at an identical angle and nearly at a weftwise level, rendering the final fabric laterally dense. Such mode of formation is undesirable for practical purposes as it is rather tedious and complicated, less productive and yet susceptible to quality irregularities and cost burdens.